The present invention relates to a material with diamonds dispersed in a matrix of hard constituents and binder phase and a method of making the same. The material can be used for chip forming machining as well as rock drilling products and wear parts.
Cemented carbide is a material used in industry for a great number of applications as a cutting and wear-resistant material. Cemented carbide consists of hard constituents of WC, TiC, NbC and/or TaC embedded in a binder phase based upon Co, Ni or Fe. The amount of binder phase is typically 5-25% by weight. Cemented carbide is made by powder-metallurgical methods, i.e., milling, pressing and sintering.
A growing group of materials being used essentially for finishing are titanium-based carbonitride alloys, colloquially named cermets. The hard constituent of these alloys is mainly cubic phases of TiC-TiN completely or partly alloyed with other elements such as W, Mo, Ta, Nb, etc. The hard constituents are usually present as more or less rounded particles having a core-rim structure in a binder phase based upon Co, Ni or Fe, usually Ni+Co.
Diamond has, because of its high hardness, been of great interest as an element in wear-resistant materials, Many techniques have been tested for incorporating diamond in a matrix to obtain a dense material. The great problem is, however, the insufficient thermal stability of diamond at high temperatures and normal pressures. High pressure methods have so far been considered necessary to obtain a good result. In general, the diamond is applied as a layer upon a finished substrate usually of cemented carbide in such a process that the diamond does not decompose to graphite, thus losing its good properties.
Diamond layers can also be precipitated on, e.g., cemented carbide at low pressure from gaseous phase by using a gas mixture of hydrogen and a hydrocarbon.
Materials consisting of uncoated diamonds in a cemented carbide matrix are disclosed in a number of older patents. U.S. Pat. No. 1,996,598 discloses a material in which one volume part of diamond particles is embedded in a matrix of 3-4 volume parts of WC-Co in which the Co content is 3-25%. Great Britain Patent No. 611,860 discloses 20-25% by volume of diamond embedded in a matrix of WC and 3-25% Co. Sintering is done under a pressure of 70 kg/cm.sup.2 at a temperature of 1350.degree.-1380.degree. C. Great Britain Patent No. 531,077 discloses a matrix of 2.5-5% TiC, 9-15% binder phase and the rest WC. In German Patent No. 767,569 there is described a compound body consisting of a core of diamond-containing matrix of carbides from groups IV, V and VI surrounded by a diamond-free cover of the same composition as the matrix in the core or otherwise. Swedish Patent No. 192,637 discloses a rock drilling insert with &gt;85% WC, &lt;5% other carbides as TiC and TaC, 6-10% binder phase and possible other hard constituents such as diamond.